The present invention relates to a liquid reagent of a thyroid hormone-immobilized carrier and use thereof, specifically a method for stabilizing a thyroid hormone-immobilized carrier in a solvent, a method for producing the liquid reagent, and a method and kit for detecting a thyroid hormone.
The thyroid hormones are hormones secreted from the thyroid and have an effect of improving a metabolic rate of cells of a whole body by acting on the cells. As the thyroid hormones, for example, triiodothyronine (T3) and thyroxine (T4) are known. Patients having thyroid dysfunctions such as hyperthyroidism (e.g., Basedow disease) caused by excessively secreting thyroid hormones, hypothyroidism (e.g., Hashimoto disease) caused by lack of secretion of thyroid hormones, and the like have been increased in recent years. Therefore, it is important to accurately measure the thyroid hormones in clinical examinations and the like.
In order to measure the thyroid hormones, for example, competitive immunoassay using an anti-thyroid hormone antibody has been widely employed (see JP H9-89889 A, 2010-53118 A, and Kathmandu University Medical Journal (2005), Vol. 3, No. 1, Issue 9, pp. 91-93). The measurement system of this competitive immunoassay is that thyroid hormones in a sample and those in a reagent are competitively reacted with anti-thyroid hormone antibodies. In the competitive immunoassay, a three-reagent kit is generally used. The kit is composed of a labeled antibody as a first reagent, a biotinylated thyroid hormone as a second reagent, and an avidin-immobilized carrier as a third reagent, and the reagents are stored individually. The measurement using the three-reagent kit is carried out as follows, for example. That is, first, a sample and a labeled antibody are mixed with each other so that a thyroid hormone in the sample and the labeled antibody are bound to each other. Thus, a mixture is obtained. Then, a biotinylated thyroid hormone and an avidin-immobilized carrier are mixed with the mixture. Whereby, a composite of an unreacted labeled antibody that has not been bound to the thyroid hormone in the sample, the biotinylated thyroid hormone, and the avidin-immobilized carrier is formed by an antigen-antibody reaction and an avidin-biotin bond. Thereafter, the composite is separated, and the labeled antibody in the composite is detected. The thyroid hormone in the sample and the biotinylated thyroid hormone are competitively bound to the labeled antibody. Therefore, the labeled antibody binding to the thyroid hormone in the sample can be measured by detecting the labeled antibody in the composite. Whereby, the thyroid hormone in the sample can be measured indirectly. However, in the measurement using the three-reagent kit, it is necessary to mix the three reagents every time the measurement. Therefore, an operation becomes complicated, requires time, and involves a high cost.